Passive Electronic Components - Capacitors.

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Passive ComponentsCapacitors

• CEC

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Contents

• Introduction.
• Capacitor Classifications.
• Fixed Capacitors.
• Variable Capacitors.
• Capacitor Coding.
• Super Capacitors.
• Applications.

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Capacitors

• Passive electronic component.
• Capacitance expressed in Farads.
• Metal plates separated by dielectric.
• Impedance has reactive components.
• Frequency dependent reactance.
• Can store and release energy.
• Blocks dc and passes ac.
• Opposes change in voltage.
• With or without polarity.

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Breakdown Voltage

• Voltage above which the dielectric will breakdown
  and start conducting.
• Depends on the type of the capacitor.

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Capacitor Types

Capacitors

Fixed Capacitors
Variable Capacitors
Gang Condensor
Ceramic Disc
Trimmer
Electrolytic
Padder
Ceramic Tubular
Tantalum
Paper
Mica
Polyester
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Capacitor Symbols

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Electrolytic Capacitors

• Polarised, has positive and negative electrodes.
• Aluminium foil electrodes with aluminium oxide
  film covering on one side.
• Oxide as dielectric, aluminium plates as
  electrodes.
• Oxide in contact with paper saturated with an
  electrolyte.
• Electrolyte as the second plate.

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Electrolytic Capacitors

• Layer of aluminium without oxide for electrical
  contacts.
• 1µF to a few thousand µF, 1V to 500 V.
• Size depends on voltage rating.
• As filters in power supplies, coupling capacitors.

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Electrolytic Capacitors

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Tantalum Capacitors

• Electrolytic, tantalum electrodes.
• Polarised.
• Superior to electrolytic capacitors in
  temperature and frequency characteristics.
• Expensive.
• Stable capacitance values.
• Used in analog signal systems.

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Tantalum Capacitors

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Mica Capacitors

• Mica as dielectric, flat strips of metal foil
  separated by mica.
• Metal plates connected to two electrodes.
• Relative costly.
• 5 to 10,000 pf, up to 500 V, no polarity.
• Excellent frequency characteristics.
• Used in resonance circuits and high frequency
  filters.
• Good insulation, in high voltage circuits.

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Mica Capacitors

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Ceramic Capacitors

• Titanium and barium as dielectric.
• Ceramic disc with silver or copper plating on
  opposite faces.
• Leads attached to the plates.
• In high frequency applications.
• In both ac and dc circuits.
• As byepass capacitors.
• 3 pF to 2 µF, no polarity.

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Ceramic Capacitors

Disc
Tubular
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Paper Capacitors

• Two metal foils separated by strips of paper.
• Paper impregnated with wax, plastic or oil
  (dielectric).
• 0.0005 µF to several µF.
• No polarity.
• 100 Volts to several thousand Volts.
• More bulky.

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Paper Capacitors

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Variable Capacitors

• Capacitors for coarse and fine adjustments.
• Used for frequency adjustments.
• In radio tuners, tuning to a radio station.

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Gang Capacitors

• Group of capacitors ganged together.
• Air Gang and PVC Gang.
• Rotor-Stator type variable capacitor with two
  sets of metal plates.
• Fixed plates connected together to form stator.
• Movable plates connected together on a rotating
  shaft.
• In radio receivers to tune to stations.

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Gang Capacitors

PVC Gang
Air Gang
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Trimmers

• Mica or Ceramic as dielectric.
• Capacitance varied by turning adjustment screw.
• Normally initial setting undisturbed.
• Low values of the order of pF.
• Use when frequent adjustment is not required.
• Use in TV, broadcast receivers.

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Trimmers

Trimmers
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Padders

• Higher capacitance values.
• Two concentrically mounted tiny aluminium cups.
• Air as dielectric.
• Gap between two caps varied by turning a screw,
  capacitance varies.
• 5 pF to 600 pF.

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Padders

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Super Capacitors

• High capacitance values.
• Uses electrostatic double-layer capacitance and
  electrochemical pseudocapacitance.
• 10 to 100 times more energy per unit volume than
  electrolytic capacitors.
• Bridges the gap between electrolytic capacitors
  and rechargeable batteries.
• Used in applications requiring many rapid
  charge/discharge cycles.

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Super Capacitors

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Indicating Capacitance Values

• Alphanumeric and colour coding schemes.
• Value written in coded form on small capacitors.
• Similar to resistor colour coding scheme.
• Five colour bands - value (first two bands),
  multiplier (third band) and tolerance (fourth
  band).
• Fifth band indicates voltage rating.

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Alphanumeric Coding
Code 0.1 10 104 10k
Value 0.1µF 10 pF 10 x 104 pF (0.1 µF) 10 kpF (0.01 µF)
Code 10n 1M 2M2 4k7
Value 10 nF 1 µF 2.2 µF 4.7 kpF (0.0047 µF)
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Alphanumeric Coding

• If the number written is greater than 1, value in
  pF, else in µF.
• For 3 digits, 3rd digit indicates multiplier.
• If letter k follows digits, value in kpF.
• If n or M, value in nF or µF.
• k or M follow a 3 digit number implies 10
  and 20 tolerance.
• If n, M or k between numbers, put decimal
  point in place, value in nF, µF or kpF
  respectively.

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Alphanumeric Coding

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Capacitor Colour Coding
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5 band system
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Capacitor Colour Coding

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Capacitor Colour Coding

Identify the above capacitors
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Capacitor Applications

• As timing elements in oscillator circuits.
• Coupling - to block dc and pass ac signals.
• Byepass to byepass high frequencies.
• Surge suppression.
• In filter circuits.
• In clampers and voltage multipliers.
• In differentiating and integrating circuits.

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Thank You